Physico-Chemical Attributes

Monitoring Distribution and Abundance at Broad Scale

Monitoring Distribution and Abundance at Intermediate Scales

Monitoring Distribution and Abundance at a Local Scale

Monitoring Individual Reefs

A number of physical and chemical parameters could usefully be recorded in areas of Sabellaria alveolata reef. In particular, these would include coastal water and air temperatures, which may influence growth and fecundity, wave action, and sand distribution/levels, a supply of suspended coarse sand being essential for the formation of the tubes. It would be particularly important to record the latter in areas where coastal developments with the potential to change sediment transport and deposition are likely.

Monitoring and surveillance has to be undertaken at the hierarchy of spatial and temporal scales. At the broadest and longest scale the distribution of Sabellaria alveolata should be re-surveyed decadally using Cunningham et al. (1984) as a baseline. Using the broadscale biogeographic approach adopted by Crisp & Southward (1958) and rapid semi-quantitative abundance scales (see Cunningham et al., 1984), the extent of this organism can be rapidly surveyed. Contractions or extensions in range can be mapped and increases in abundance within its range tested using a matched set test (e.g. Friedman’s test matching by site over time). For example recent observations at Lyme Regis have shown an increase in the sheet-like reef in recent years which was not detected by Cunningham et al. (1984) in the early 1980s, despite frequent visits by one of the authors (S.J.H.) during this period. The methods to be used are simple and could readily be adopted by County Wildlife Trusts and EN, SNH, CCW regional staff with modest training. Alternatively the resource required would be about 3 months person-time plus travel and subsistence.

The extremely broadscale approach described above could be supplemented by more detailed observations using low level aerial photography, (or alternatively fixed viewpoint photography, although this gives more problems in calculating area covered) at low tide. Ideally these should be done annually, because the highly variable nature of S. alveolata reefs means that considerable amounts of data would be required to identify trends in abundance. Limited ground truthing would be required and such an approach can be tested using recently acquired aerial photographs of the Cumbrian/Solway coast (Lumb, pers. comm.), since it is not clear how obvious Sabellaria reefs are on aerial photographs. A relatively recent survey (Allen et al., 1991) has also been undertaken on a number of transects on this stretch of coast. Percentage cover estimates were made at 0.5 m vertical intervals in one of two ways: by visual estimates of percentage cover of a 5 m wide band, or by estimates from each of 15 to 25 replicate quadrats. Repeats of these surveys would allow some estimates of change to be measured whilst ground truthing.

The next level of detail would be to choose groups of adjacent sites within a region (e.g. three shores at each of Galloway, Cumbria, Cardigan Bay, S. Wales, N. Cornwall, S. Devon) and undertake quantitative work at each site. This would enable separation of local effects (beach movements, trampling, failure of local recruitment) from more widespread effects (e.g. the effects of climate on reproductive output). On each shore three sub-areas of Sabellaria habitat would need to be selected. The abundance of Sabellaria could be assessed quantitatively by stretching 25m long tapes parallel to the shore line and scoring the number of times Sabellaria is found under every half metre (50 intersection points). An hierarchical analysis of variance could be used to separate regional, local (between shores) and within shore variation. This approach could be coupled with biotope mapping on stretches of shore, whole shore photographs, photographs of areas, plus qualitative descriptions of types of colony. Using a video recorder would be an excellent way of retaining these records.

More detailed studies could focus at the individual reef level at selected key sites within cSACs. This level of detail would be particularly good for looking at the growth, development and senescence of reefs and their associated flora and fauna. Much useful background exists in the work of Wilson (1971) and Gruet (Gruet, 1977; Gruet, 1981; Gruet, 1982; Gruet, 1985; Gruet, 1986; Gruet, 1989) but this was largely autecological and not very quantitative. There is a need to measure rates of colony growth and decay. The approach to be adopted would be to mark out replicated reefs in various stages of growth or senescence (after Wilson, 1971). These would be measured and mapped. The associated flora and fauna could be qualified non-destructively using replicated small 0.25 x 0.25 quadrats thrown on the reef. Wilson (1971) also reported that the use of a skewer inserted between adjacent tubes in order to measure the thickness of a colony resulted in no apparent harm. This simple method could be used in order to compare growth rates.

For detailed studies of intertidal growth rates, Bamber & Irvine (1997) successfully attached substantial pieces of S. alveolata reef (c. 1.5 l volume) to plywood bases using epoxy resin. These were cured overnight in seawater and then screwed to larger plywood sheets which were themselves screwed onto the bedrock on the shore. This system appears to have been used successfully for over a year. The reefs were periodically removed and the volume measured by the displacement of water. Calculation of the volume using measurements obtained by photography gave a consistently larger estimate compared to the displacement volume.

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